Musnad Ahmad 25:1290

Hajjaj narrated to us, Shu'bah narrated to us, from Qatadah, who said: I heard Abu Hassan al-A'raj narrating from Ibn Abbas, who said: "The Messenger of Allah (peace and blessings of Allah be upon him) prayed Dhuhr at Dhu al-Hulayfah. Then a sacrificial camel was brought to him, and he marked the right side of its hump, wiped the blood from it, and garlanded it with two sandals. Then he called for his riding beast and mounted it. When it stood upright with him upon the desert (al-Bayda'), he began the talbiyah for Hajj."